This research is designed to obtain detailed information about the molecular structure of pituitary growth hormone, prolactin, and related proteins of the pituitary and placenta, and to determine relationships between structure and biological activity. With completion of the sequence analysis of bovine growth hormone, studies are now directed toward the structural study of bovine prolactin and subprimate growth hormones. Additional effort is directed toward isolation and eventual sequence analysis of placental lactogens from bovine and ovine sources. Data on the primary structures will be used to examine homologies and evolutionary relationships with growth hormones and prolactins of other species and to search for potential homologies with other hormonal proteins. In collaborative studies, the biological activity of fragments of growth hormone and prolactin produced with cyanogen bromide and other specific cleavage reagents will continue to be evaluated to an attempt to define the area or areas of these molecules which are responsible for binding to target cells or constitute active sites or centers. Use will be made of specific radioreceptor assays for prolactin and growth hormone in mammary tissue and liver respectively as an index of biological specificity and activity. Growth hormone and prolactin covalently linked to Sepharose and other isoluble supports will be investigated as tools for exploring the interaction of these proteins with small molecules and macromolecular components of cell membranes and also to isolate specific antibodies for immunochemical studies. Studies will be carried out on the large scale isolation and characterization of membrane receptors from bovine and ovine mammary tissue and liver in order to initiate the investigation of the structure of growth hormone and prolactin binding proteins. Studies will also be carried out to investigate the effects of growth hormone, prolactin and placental lactogens on enzymatic activities and macromolecular synthesis during development of the central nervous system.